P.S.
Adding just these two lines to modprobe.conf
softdep bttv post: lirc
softdep dvb_bt8xx post: lirc
on the machine whose dmesg I just posted above that failed (gx110)
It worked! So clearly a race condition. Racing with what, I don't know.

With this working dmesg trace, to compare against the previous bad one
(same machine)

[ 0.119942] system 00:00: iomem range 0x100000-0xffffff could not be
reserved
[ 0.120014] system 00:00: iomem range 0x1000000-0xfeabfff could not
be reserved
[ 0.120103] system 00:00: iomem range 0xf0000-0xfffff could not be
reserved
[ 0.120174] system 00:00: iomem range 0xffb00000-0xffbfffff has been
reserved
[ 0.120246] system 00:00: iomem range 0xffc00000-0xffffffff has been
reserved